Asking Labour supporters to “let me do a job for you”, she insisted the Conservatives are “rooted to the centre ground” and argued that the Tories can “lead the fightback against the SNP.”

In a direct message to Ms Sturgeon, she said: "The PM says she is a bloody difficult woman, well you ain't seen nothing yet."

Speaking on BBC Breakfast this morning, Ms Sturgeon said: "Every poll that's published in Scotland shows that the SNP is on course to win this election and win it comprehensively.

"The Tories are doing better, there's no getting away from that. They're doing better largely at the expense of Labour.

"What we've seen over the past few years in Scotland is a collapse in the Labour vote - much of it has turned to the SNP - we're now seeing Labour lose a lot of its remaining support to the Conservatives.

Ruth Davidson gives a speech during the launch of the Scottish Conservative manifesto in EdinburghCredit:
RUSSELL CHEYNE

"This is a Westminster election, it's about who represents Scotland at Westminster.

"Tory MPs from Scotland will be rubber-stamps for whatever Theresa May wants them to do, so if we want to have strong voices of opposition standing up for Scotland given the big challenges that lie ahead, then we need to make sure that there are SNP voices doing that."

Speaking at the launch of the Scottish Tories manifesto, Mrs May said: "Only the Conservative and Unionist Party has the strength and credibility to stand up to the Nationalists and defend our United Kingdom."